****************************************************************************** DORIS Electronic Mail Fri Jun 25 18:03:49 WETDST 1999 Message Number 0075 ****************************************************************************** Author: Gilles Tavernier (CNES) Subject: DIODE/SPOT4 results after more than a year SPOT4 was launched one year ago, on March, 24th 1998. Following SPOT2, TOPEX/POSEIDON and SPOT3 this is the fourth spacecraft fitted out with a DORIS receiver. The SPOT 4 receiver includes a new feature : the DIODE navigator, which calculates a real-time on-board orbit. Activated on March, 26th 1998, DIODE was tested until April, 10th 1998 and is fully operational since than DIODE has now been operating for more than one year, producing reliable and precise results : - the accuracy is: - 2.7 m RMS for the radial component, - 4.0 m RMS for the along-track component, - 3.0 m RMS for the cross-track component, - the availability is over 99.4 percent since April, 10th 1998: - one single DIODE incident on July, 4th 1998 - continuously operating for 11 months - one DORIS incident on June, 3rd 1998 - continuously operating since then - 100% reliable with regard to requirements, when operating After one year, the DIODE concept is fully validated and further applications can be considered such as : - total or partial autonomous orbit control - station keeping costs reduction - real time monitoring of maneuvers - terminal pointing This success is the fruit of several contributions, in particular : - CNES Research and Technology programs, which funded the development - Precise Orbit Determination people from CNES Flight Dynamics Division who thought this new DORIS application up and achieved it - SPOT 4 project, which proposed to take DIODE on board and to use its products - The DORIS system, more particularly its network, operating for nearly ten years now, thanks to IGN/SIMB (IGN's DORIS beacons installation and maintenance department) and every organization hosting beacons all over the world. To every actor of this achievement: congratulations and thank you! An improved version of DIODE, already tested and validated will fly on-board ENVISAT, JASON and SPOT5 spacecraft : - the accuracy will be better than 1 meter RMS 3D - the autonomy will be increased thanks to auto-start and self-programming It is thus possible to offer efficient navigation possibilities to spacecraft currently being designed, especially for constellations of Low Earth Orbiting satellites of any type. Gilles TAVERNIER _____________________________________________________ CNES DSO/ED/AL/MA - Bpi 2002 Phone : 33 - (0)5 61 27 37 76 18, avenue Edouard Belin Fax : 33 - (0)5 61 28 25 95 31 401 TOULOUSE CEDEX 4 Email : Gilles.Tavernier@cnes.fr=20 _____________________________________________________ [Mailed From: Pascal Willis ]